Having a few Raspberry Pi 4s at my disposal, I found myself somewhat dissatisfied with their processing capabilities and power management features. This led me to explore alternative solutions, particularly given the collection of old smartphones gathering dust in my drawer. These devices, while outdated for daily use, still pack considerable computing power. In this article, I’ll walk through how I transformed these old smartphones into a functional Kubernetes cluster using postmarketOS, giving them a second life as computing nodes.